public class code {
    //合并两个有序链表
    //迭代
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        ListNode ret = new ListNode();//骷髅结点
        ListNode cur = ret;//遍历
        while(list1!=null&&list2!=null) {
            if(list1.val<list2.val) {
                cur.next = list1;
                list1 = list1.next;
            } else {
                cur.next = list2;
                list2 = list2.next;
            }
            cur = cur.next;
        }
        if(list1!=null) cur.next = list1;//剩下的接上
        if(list2!=null) cur.next = list2;
        return ret.next;
    }
}
